1. Field of the Invention
The present invention relates to an instant camera. More particularly, the present invention relates to an instant camera of which a structure is simplified.
2. Description Related to the Prior Art
An instant camera is a camera with which a photograph can be obtained immediately after an object is photographed. The instant camera is loaded with a film pack, which contains a plurality of self-processing instant film units of a mono-sheet type stacked on one another. Each film unit has an image-recording portion, a pod portion disposed on an edge and containing processing solution, and a trap portion disposed opposite to the pod portion for absorbing surplus of the processing solution after being spread. The instant camera incorporates a known claw mechanism, which advances the foremost of the film units after being exposed. The exposed film unit is exited through a top of a body of the camera. The spreading rollers in the camera body rupture the pod portion, and spread the processing solution over the image-recording portion. With the film unit exited from the camera, the processing solution has finished being spread. The film unit is left to stand for a predetermined duration, to become a photographic print as completed.
The film pack consists of a plastic cartridge or case shaped like a box and a plurality of film units stacked on one another. A back wall of the cartridge has an exposure aperture. A top side of the cartridge has an exit slot for the film units. The inside of the back wall of the cartridge has a pressure plate, which presses the film units against a front wall of the cartridge, and flattens the film units directly behind the exposure aperture or front wall. The film pack in the unused state also contains a light-shielding plate lapped on the foremost of the film units to close the exposure aperture light-tightly. A flap as light-shielding member is mounted in the exit slot, to protect the inside of the film pack from ambient light.
When the loading chamber of the instant camera is loaded with the film pack, the claw mechanism contacts and advances a light-shielding plate, which has protected the film units from ambient light. The light-shielding plate is ejected by the spreading rollers. In exiting of the light-shielding plate, the plate is thrust into a flap, which has been disposed in an exit slot. The light-shielding plate has directly covered the first or foremost of the film units. The foremost film unit is pressed by the pressure plate, and positioned on the exposure aperture, to stand by for photography.
Prior to the photography, the flap must be pushed and torn by the initially advanced light-shielding plate. Accordingly the claw mechanism moving the light-shielding plate requires sufficient drive force. The complicated spreading mechanism is conventionally used with a motor having a great torque. However the motor having the great torque is so expensive as to raise the cost of the camera. When all the film units in the film pack are used, the film pack cartridge or case, and the light-shielding plate remain as waste, of which disposal is a problem in environmental view.
There is a commercially available lens-fitted photo film unit sold with a trade name "Fujicolor Quick Snap" (manufactured by Fuji Photo Film Co., Ltd.), which is a single-use camera pre-loaded with unexposed 35 mm negative film. It is conceivable to construct an instant camera as a single-use type like this lens-fitted photo film unit. However, many problems arise with such conception. The use of the film pack enlarges the size of the single-use instant camera, and raises the cost of manufacturing the camera.
In the conventional instant camera, the film units are pressed by a pressure plate toward the front to be kept flat on an exposure aperture. However, the conventional pressure plate has failed to flatten the film units in reliable fashion, as each film unit has the pod portion and trap portion both projected toward the front over the level of the image-recording portion.
While a body of the instant camera includes a film pack loading chamber and a drive mechanism for driving a claw member and spreading rollers, the body is provided with a light-shielding tunnel, with which an exposure opening and the taking lens are associated. An image-recording portion of each film unit is considerably larger than a counterpart of a 35 mm negative film. This results in the greater distance defined between the taking lens and the film unit as positioned, in view of exposure on the larger area. It follows that the light-shielding tunnel has a shape projecting toward a front to a considerably great extent as compared with a camera for the 35 mm film, and seriously affects portability of the camera. In view of the portability, a widely used instant camera has foldable bellows for the light-shielding tunnel, and is collapsible with the construction having a taking lens board disposed in front of the bellows and connected to the body via the bellows. There still remains a problem: such a foldable tunnel makes it necessary for the body to have a space for containing all of the mechanisms for photography. The body is obliged to have a great size. There is no known technique for reducing the space for containing all the mechanisms in the body. In a construction of the instant camera as a single-use type, it is highly difficult to provide the foldable light-shielding tunnel as above, because it would raise the manufacturing cost of the camera.
To advance the film units to the outside of the instant camera, a claw and spreading rollers are actuated as driven by a motor via transmission mechanisms associated with the claw and the spreading rollers, as disclosed in commonly assigned Japanese Utility Model Application No. 2-109344. The claw moves until an edge of the exposed film unit opposite to the claw comes to the spreading rollers, but afterwards the claw must be returned to its home position. It is conventional to use a one-rotation detecting gear to synchronize movement of the claw. The one-rotation detecting gear makes one rotation for advancement of each film unit, and signals a time point of when to stop the motor. In the driving of the spreading rollers, a clutch mechanism is actuated to disconnect the claw from its associated transmission. Upon the finish of the exiting of the film unit, the claw is returned to its home position.
In a construction of the instant camera as a single-use type, a claw mechanism is still used for exiting of advancing the exposed film unit. However it is difficult or impossible to provide the single-use type with the one-rotation detecting gear, a one-rotation detecting base plate for detecting the gear, or the clutch mechanism for detaching the claw mechanism from the motor. A simple detector could detect a position of the claw mechanism to cause the motor to stop. However, a gear would overrun its stop position after the stop of the motor. There would occur irregularities in the stop position of the claw. The film units could not be advanced or exited in regular fashion.